In current technology, a radio frequency communication system following a specific standard is governed by a maximum audio transmission rate. A typical maximum audio transmission rate is on the order of 64,000 bits per second (64 kbps) which corresponds to high fidelity audio. However, transmission of audio signals at full rate requires a significant amount of resources in terms of power and spectrum. Thus, full rate audio transmission is not cost-efficient for applications such as mobile cellular communications, but is more suited to wireline communication systems or high-power directive microwave links where these parameters are not as critical.
In addition, for mobile cellular communication systems, the predominant use is for voice communication such as conversations between parties via radiotelephones. For simple voice communication, high fidelity audio is not critical for efficient communication. The human ear is capable of discerning audio signals at much lower resolution. In these instances, audio transmission rates on the order of 3,200 bits per second (3.2 kbps) may provide sufficient audio quality for the parties to the conversation. Communication at this level results in significant conservation of power and spectrum resources for the communication system. However, there may be instances where high fidelity audio is required, for example, where a musical recording must be transmitted. The problems lies in that the audio transmission rate is determined when the audio signal is coded and the coding device typically is set to code the signal at a single predetermined rate. Thus, there exists a trade-off between conservation of power and spectrum resources at a low transmission rate and providing an acceptable audio resolution to the system user at a high transmission rate. Therefore, a system is needed to eliminate this trade-off whereby the resolution or the quality of an audio signal transmitted via radio frequency communication systems can be varied by the users to meet specific situations.